1. Field of the Invention
The present invention relates to a disk array apparatus incorporating a plurality of disk units and a method of controlling the disk array apparatus.
2. Description of the Related Art
As a technique for improving the speed of access to data and the reliability of a disk array apparatus by providing a plurality of disk units, the redundant array of independent disks (RAID) has been known. Typically, a disk array controller is responsible for the RAID control, and the performance improvement of the disk array controller has been pursued.
The disk array controller has a CPU for executing a processing program for the array controller. According to an approach to the performance improvement, a plurality of CPUs are mounted on the disk array controller to enable parallel processing, thereby increasing the processing speed.
[Patent Document 1] Japanese Patent Publication No. 09-160889
[Patent Document 2] Japanese Patent Publication No. 06-35871
However, the disk array apparatus having a plurality of CPUs requires an expensive shared memory to share information among the CPUs. Thus, the cost is high relative to the performance improvement, and there is a problem that the cost-performance is reduced. In addition, since each CPU requires a clock or a power supply circuit, the assembly is enlarged, and thus, the production cost also increases.
As for the control, according to the technique disclosed in the Japanese Patent Publication No. 9-160889, a processing is allocated to a control processor or a group of processors on a job basis. In this case, plural divisional controls (jobs) reside in one processor or a group of processors. Therefore, if the system management function of the disk array apparatus goes down due to a security crack or the like, for example, it may cause another function to go down.